1. Field of the Invention
The present invention relates to an implantable heart stimulating device, a system including such a device and a method for heart stimulation using the system. More precisely, the invention concerns a stimulating device of the type having a housing and a control circuit arranged in the housing. The heart stimulating device is designed such that it can be used to stimulate both ventricles of a heart.
2. Description of the Prior Art
Most heart stimulating devices, or pacers, are designed to stimulate the right ventricle of the heart. It is also known to stimulate the left ventricle. In particular for the treatment of congestive heart failure (CHF) or other severe cardiac failures, it is known to stimulate the left ventricle, or both ventricles, in order to optimize the hemodynamic performance of the heart.
U.S. Pat. No. 5,720,768 describes different possible electrode positions in order to stimulate or sense the different chambers of the heart.
In different kinds of heart stimulating devices it is also known to use an impedance value in order to control different pacing parameters.
U.S. Pat. No. 5,154,171 describes the use of impedance values to control the pacing rate. The pacer described in this document is designed only to stimulate the right side of the heart.
U.S. Pat. No. 6,070,100 describes that electrodes may be positioned in both the left atrium and the right atrium as well in the left and the right ventricles. The patent describes the possibility of sensing the impedance between different electrodes. The sensed impedance values may be used to improve the cardiac output.
United States Patent Publication No. 2001/0012953 describes bi-ventricular pacing. An impedance may be measured between electrodes on the right and the left sides of the heart. The variation of the impedance with time is detected. The detected impedance variation may be used in order to synchronize the contraction of the ventricles.
United States Patent Publication No. describes different manners of using the proximal and distal electrodes of different leads in order to inject a current and to measure an impedance. The measured impedance value may be used in order to maximize the cardiac flow.
For a patient suffering from congestive heart failure (CHF) it is of a great benefit to be able to increase the cardiac output, thereby decreasing the degree of CHF. One cause of CHF is that the left and right ventricles are not synchronized with each other. By optimising the synchronization between the ventricles, the filling of the ventricles and the cardiac output may be increased.